Individual submission                                       M. Kucherawy
Internet-Draft                                             June 17, 2014
Updates: 7001 (if approved)
Intended status: Standards Track
Expires: December 19, 2014

 A Property Types Registry for the Authentication-Results Header Field


   [RFC7001] describes a header field called Authentication-Results for
   use with electronic mail messages to indicate the results of message
   authentication efforts.  Any receiver-side software, such as mail
   filters or Mail User Agents (MUAs), can use this header field to
   relay that information in a convenient and meaningful way to users,
   or make sorting and filtering decisions.

   One portion of the definition in that document limits the types of
   authentication properties about a message to a small, fixed set.
   This document updates the specification to allow new property types
   to be declared and used.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 19, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents

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   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Updated 'ptype' Definition  . . . . . . . . . . . . . . . . . . 3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . . . 5

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1.  Introduction

   [RFC7001] describes a header field called Authentication-Results for
   electronic mail messages that presents the results of a message
   authentication effort in a machine-readable format.  The intent of
   the header field is to create a place to collect such data when
   message authentication mechanisms are in use so that a Mail User
   Agent (MUA) and downstream filters can make filtering decisions
   and/or provide a recommendation to the user as to the validity of the
   message's origin and possibly the safety and integrity of its

   The specification in that document enumerated a small set of types of
   properties that can be reported using this mechanism.  There has
   emerged a desire to report types of properties about a message
   through this mechanism.  Accordingly, this document updates the
   specification to allow for additional property types ("ptypes")
   beyond the original set, and creates a registry where new ones can be
   listed and their defining documents referenced.

2.  Updated 'ptype' Definition

   Advanced Backus Naur Form (ABNF) is defined in [RFC5234].

   The ABNF in Section 2.2 of [RFC7001] is updated as follows:

       ptype = Keyword
             ; indicates whether the property being evaluated was
             ; a parameter to an [SMTP] command, was a value taken
             ; from a message header field, was some property of
             ; the message body, or was some other property evaluated by
             ; the receiving MTA

   The ABNF token "Keyword" is defined in Section 4.1.2 of [RFC5321].

   Legal values of "ptype" are as defined in this document, or in the
   IANA "Email Authentication Property Types" registry (see Section 3).
   The initial values are as follows, matching those defined in

   body:  Indicates information that was extracted from the body of the
      message.  This might be an arbitrary string of bytes, a hash of a
      string of bytes, a Uniform Resource Identifier, or some other
      content of interest.

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   header:  Indicates information that was extracted from the header of
      the message.  This might be the value of a header field or some
      portion of a header field.

   policy:  As defined in Section 2.3 of [RFC7001].

   smtp:  Indicates information that was extracted from an SMTP command
      that was used to relay the message.

   A consumer of this header field encountering a "ptype" it does not
   understand simply ignores the result it is reporting.

3.  IANA Considerations

   IANA is requested to create the Email Authentication Property Types
   registry.  Entries in this registry are subject to the Expert Review
   rules as described in [RFC5226].  Each entry in the registry requires
   the following values:

   o  The "ptype" token to be registered, which must fit within the ABNF
      described in Section 2.

   o  A brief description of what sort of information this "ptype" is
      meant to cover.

   o  A reference to the defining document, if any.

   The initial entries in this table are enumerated in Section 2.  This
   document should be listed as their defining document values.

   For new entries, the Designated Expert simply needs to assure that
   the description provided for the new entry adequately describes the
   intended use.  An example would be helpful to include, although
   entries in the Email Authentication Methods registry or the Email
   Authentication Result Names registry might also serve as examples of
   intended use.

4.  Security Considerations

   A consumer of this header field might be confused by a result bearing
   a "ptype" it does not understand.  The advice is simply to ignore
   such a result since its semantics are unknown to such a consumer.  It
   is unknown how legacy code, which expects one of a fixed set of
   "ptype" tokens, will handle new tokens as they begin to appear.  This
   could conceivably result in undesirable deliveries for consumers that
   have been implemented to "fail open".

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5.  Normative References

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              October 2008.

   [RFC7001]  Kucherawy, M., "Message Header Field for Indicating
              Message Authentication Status", RFC 7001, September 2013.

Appendix A.  Acknowledgements

   The author wishes to acknowledge the following for their review and
   constructive criticism of this update: (names)

Author's Address

   Murray S. Kucherawy
   270 Upland Drive
   San Francisco, CA  94127


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